Apatite: A proxy to study ore deposits?
Résumé
Apatite (Ca5(PO4)3(OH, F, Cl)) is an ubiquitous
accessory mineral found in many types of rocks and
environments. This mineral has several key features
for the characterization and/or the dating of fluid
circulation or magmatism responsible for the
emplacement of mineralization:
1. It often incorporates uranium during its
crystallization. This makes it an excellent candidate
for U-Pb dating. Moreover, apatite can also be dated
by the fission tracks and (U-Th)/He methods.
Therefore the same mineral can bring information on
the age of the mineralization and its exhumation
history.
2. Apatite is an excellent trap for the P, F, Cl,
OH, but also for Rare Earth Elements (REE) [1].
3. This mineral can easily react in the presence of
brines, or aqueous fluids containing CO2, HCl, H2SO4
and/or F [2].
4. In many ore deposit, the crystallization of
apatite is contemporaneous with mineralization
processes [3].
5. Its closure temperature with respect to the UPb
system (375-550°C) gives it a peculiar role for
dating hydrothermal events [4].
Accordingly, apatite is, a priori, an excellent
proxy for obtaining extensive information about
mineralizing fluids and/or fertile magmas
(temperatures, compositions and ages or durations of
the events), information that is essential for
establishing a metallogenic model.
We will present a comprehensive set of CL
imaging, EPMA analyses, SIMS stable isotopes and
U-Pb dating on apatite from several ore deposits in
order to assess the potential of this mineral for the
study of ore deposits.
[1] O’Really & Griffin & (2000). Lithos, 53, 217-
232. [2] Pan & Fleet (2002). Rev in Mineral and
Geochem, 48, 13-49. [3] Nyström & Henriquez
(1994). Econ. Geol. 89, 820–839. [4] Blackburn et al.
(2011). Contrib. Miner. Petrol. 162, 479–500.